Which of the Following Explains Why the Quantity of a Good

Which of the following explains why the quantity of a good demanded decreases when its price increases?

A) Consumer preferences change when the price of a good changes.
B) The nominal income of consumers falls when the price of a good increases.
C) Substitutes become relatively cheaper when the price of a good increases.
D) Complements become relatively cheaper when the price of a good increases.
E) None of the above provides a reasonable explanation.